The objectives of this contract are to provide a facility where the pathogenesis of enteric diseases can be studied and candidate vaccines for these diseases can be evaluated. The contractor will recruit adult volunteers from the community, screen them for appropriate immune status, instruct them about the protocol and its objectives, perform studies on an isolation ward in the hospital, and provide appropriate follow-up for all volunteers. The studies will focus on evaluating vaccines for diseases caused by Escherichia coli, Salmonella species, Shigella species, Vibrio cholerae, Campylobacter species, rotavirus, and other enteric viruses. This facility will also be used to study the mechanisms by which these, and related, organisms cause disease. Specifically, organisms will be genetically altered and tested for their resultant virulence. These molecular pathogenesis studies will help define the biological basis of enteric disease. This facility will also serve as a focus for basic clinical investigation of the mucosal immune system and its role in protection against the diseases cause by enteric organisms.